Commit 92cd1b5d authored by Marek Szyprowski's avatar Marek Szyprowski Committed by Greg Kroah-Hartman
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staging: ion: fix common struct sg_table related issues 



The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().

struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. It
consists of a scatterlist with memory pages and DMA addresses (sgl entry),
as well as the number of scatterlist entries: CPU pages (orig_nents entry)
and DMA mapped pages (nents entry).

It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()
function.

To avoid such issues, lets use a common dma-mapping wrappers operating
directly on the struct sg_table objects and use scatterlist page
iterators where possible. This, almost always, hides references to the
nents and orig_nents entries, making the code robust, easier to follow
and copy/paste safe.

Signed-off-by: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20200619103636.11974-31-m.szyprowski@samsung.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8c589e17

drivers/staging/android/ion/ion.c

+11 −14
Original line number Diff line number Diff line
@@ -147,14 +147,14 @@ static struct sg_table *dup_sg_table(struct sg_table *table) 
	if (!new_table)

		return ERR_PTR(-ENOMEM);



	ret = sg_alloc_table(new_table, table->nents, GFP_KERNEL);

	ret = sg_alloc_table(new_table, table->orig_nents, GFP_KERNEL);

	if (ret) {

		kfree(new_table);

		return ERR_PTR(-ENOMEM);

	}



	new_sg = new_table->sgl;

	for_each_sg(table->sgl, sg, table->nents, i) {

	for_each_sgtable_sg(table, sg, i) {

		memcpy(new_sg, sg, sizeof(*sg));

		new_sg->dma_address = 0;

		new_sg = sg_next(new_sg);
@@ -224,12 +224,13 @@ static struct sg_table *ion_map_dma_buf(struct dma_buf_attachment *attachment, 
{

	struct ion_dma_buf_attachment *a = attachment->priv;

	struct sg_table *table;

	int ret;



	table = a->table;



	if (!dma_map_sg(attachment->dev, table->sgl, table->nents,

			direction))

		return ERR_PTR(-ENOMEM);

	ret = dma_map_sgtable(attachment->dev, table, direction, 0);

	if (ret)

		return ERR_PTR(ret);



	return table;

}
@@ -238,7 +239,7 @@ static void ion_unmap_dma_buf(struct dma_buf_attachment *attachment, 
			      struct sg_table *table,

			      enum dma_data_direction direction)

{

	dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction);

	dma_unmap_sgtable(attachment->dev, table, direction, 0);

}



static int ion_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
@@ -296,10 +297,8 @@ static int ion_dma_buf_begin_cpu_access(struct dma_buf *dmabuf, 
	}



	mutex_lock(&buffer->lock);

	list_for_each_entry(a, &buffer->attachments, list) {

		dma_sync_sg_for_cpu(a->dev, a->table->sgl, a->table->nents,

				    direction);

	}

	list_for_each_entry(a, &buffer->attachments, list)

		dma_sync_sgtable_for_cpu(a->dev, a->table, direction);



unlock:

	mutex_unlock(&buffer->lock);
@@ -319,10 +318,8 @@ static int ion_dma_buf_end_cpu_access(struct dma_buf *dmabuf, 
	}



	mutex_lock(&buffer->lock);

	list_for_each_entry(a, &buffer->attachments, list) {

		dma_sync_sg_for_device(a->dev, a->table->sgl, a->table->nents,

				       direction);

	}

	list_for_each_entry(a, &buffer->attachments, list)

		dma_sync_sgtable_for_device(a->dev, a->table, direction);

	mutex_unlock(&buffer->lock);



	return 0;

drivers/staging/android/ion/ion_heap.c

+13 −31
Original line number Diff line number Diff line
@@ -20,8 +20,7 @@ 
void *ion_heap_map_kernel(struct ion_heap *heap,

			  struct ion_buffer *buffer)

{

	struct scatterlist *sg;

	int i, j;

	struct sg_page_iter piter;

	void *vaddr;

	pgprot_t pgprot;

	struct sg_table *table = buffer->sg_table;
@@ -38,14 +37,11 @@ void *ion_heap_map_kernel(struct ion_heap *heap, 
	else

		pgprot = pgprot_writecombine(PAGE_KERNEL);



	for_each_sg(table->sgl, sg, table->nents, i) {

		int npages_this_entry = PAGE_ALIGN(sg->length) / PAGE_SIZE;

		struct page *page = sg_page(sg);



		BUG_ON(i >= npages);

		for (j = 0; j < npages_this_entry; j++)

			*(tmp++) = page++;

	for_each_sgtable_page(table, &piter, 0) {

		BUG_ON(tmp - pages >= npages);

		*tmp++ = sg_page_iter_page(&piter);

	}



	vaddr = vmap(pages, npages, VM_MAP, pgprot);

	vfree(pages);
@@ -64,32 +60,19 @@ void ion_heap_unmap_kernel(struct ion_heap *heap, 
int ion_heap_map_user(struct ion_heap *heap, struct ion_buffer *buffer,

		      struct vm_area_struct *vma)

{

	struct sg_page_iter piter;

	struct sg_table *table = buffer->sg_table;

	unsigned long addr = vma->vm_start;

	unsigned long offset = vma->vm_pgoff * PAGE_SIZE;

	struct scatterlist *sg;

	int i;

	int ret;



	for_each_sg(table->sgl, sg, table->nents, i) {

		struct page *page = sg_page(sg);

		unsigned long remainder = vma->vm_end - addr;

		unsigned long len = sg->length;

	for_each_sgtable_page(table, &piter, vma->vm_pgoff) {

		struct page *page = sg_page_iter_page(&piter);



		if (offset >= sg->length) {

			offset -= sg->length;

			continue;

		} else if (offset) {

			page += offset / PAGE_SIZE;

			len = sg->length - offset;

			offset = 0;

		}

		len = min(len, remainder);

		ret = remap_pfn_range(vma, addr, page_to_pfn(page), len,

		ret = remap_pfn_range(vma, addr, page_to_pfn(page), PAGE_SIZE,

				      vma->vm_page_prot);

		if (ret)

			return ret;

		addr += len;

		addr += PAGE_SIZE;

		if (addr >= vma->vm_end)

			return 0;

	}
@@ -109,15 +92,14 @@ static int ion_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot) 
	return 0;

}



static int ion_heap_sglist_zero(struct scatterlist *sgl, unsigned int nents,

				pgprot_t pgprot)

static int ion_heap_sglist_zero(struct sg_table *sgt, pgprot_t pgprot)

{

	int p = 0;

	int ret = 0;

	struct sg_page_iter piter;

	struct page *pages[32];



	for_each_sg_page(sgl, &piter, nents, 0) {

	for_each_sgtable_page(sgt, &piter, 0) {

		pages[p++] = sg_page_iter_page(&piter);

		if (p == ARRAY_SIZE(pages)) {

			ret = ion_heap_clear_pages(pages, p, pgprot);
@@ -142,7 +124,7 @@ int ion_heap_buffer_zero(struct ion_buffer *buffer) 
	else

		pgprot = pgprot_writecombine(PAGE_KERNEL);



	return ion_heap_sglist_zero(table->sgl, table->nents, pgprot);

	return ion_heap_sglist_zero(table, pgprot);

}



void ion_heap_freelist_add(struct ion_heap *heap, struct ion_buffer *buffer)

drivers/staging/android/ion/ion_system_heap.c

+1 −1
Original line number Diff line number Diff line
@@ -162,7 +162,7 @@ static void ion_system_heap_free(struct ion_buffer *buffer) 
	if (!(buffer->private_flags & ION_PRIV_FLAG_SHRINKER_FREE))

		ion_heap_buffer_zero(buffer);



	for_each_sg(table->sgl, sg, table->nents, i)

	for_each_sgtable_sg(table, sg, i)

		free_buffer_page(sys_heap, buffer, sg_page(sg));

	sg_free_table(table);

	kfree(table);

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